High strength pressure die casting alloy



United States Patent This invention relates to an aluminum alloy and particularly to pressure die casting aluminum alloys.

Pressure die casting of metal articles has economic and are of insufficient strength for many structural configurations.

These alloys must have good fluidity at casting temperatures to give good fill of the die. Also it is necessary that the alloy have little tendency to stick to the die with consequent tearing of the casting surface.

An object of the invention is an aluminum alloy of high strength which is suitable for use in pressure die casting. Other objects of the invention will become apparent in the course of the detailed description of the invention.

An aluminum alloy has been discovered which has high strength, satisfactory ductility, fluidity, freedom from die sticking and toughness such that it can be used in pressure die casting of structural configurations, such as gear housings and plant pinion carriers. This high strength aluminum alloy consists of copper, about 1.5-6.0 weight percent; iron, about, zero (0)-2.5 weight percent; magnesiu-m, about 0.161.0 weight percent; silicon, about 5-13 weight percent; zinc, about zero (0)-2.5 weight percent and the remainder essentially aluminum.

total alloy composition; amount of about 0.l5l.0 Weight percent, preferably about 0.4-0.8 weight percent; and silicon in an amount of about 5.013.0 weight percent, preferably about 7.59.5 weight percent.

While iron and zinc need not be present, i.e., their lower limit is zero (0) weight percent, it is desirable to have a pos1tive amount of each of these two metals present. Thus: iron is present in an amount of zero (0)-2.5 weight percent, preferably about 0.71.2 weight percent; and zinc is present in an amount of zero 0)-2.5 weight percent, preferably about 0.5-1.2 weight percent.

Other metals may be present in amounts typical of these aluminum alloys. For example, manganese may be present up to about 0.5 weight percent; nickel may be present up to about 0.5 weight percent. Minor amounts of other materials such as calcium, tin, titanium and the more or less usual impurities may be present. The term remainder essentially only aluminum is intended to include these other metals whether or not specifically named herein.

The hereinbefore defined aluminum alloy may-be used in any pressure die casting process. Commonly the molten metal is injected into the dies at a pressure of about 1,000-5'0,000 p.s.i.a; higher pressures may be used.

lhe strength properties of alloy of the invention are affected by the casting temperature. Although the alloy may be cast at any temperature that the metal is fluid Illustrations The strength, etc. characteristics of one embodiment of the alloy of the invention are compared to a closely similar commercial alloy. These two alloys are set out below-the aluminum contained typical metal impurities.

Invention Comparison,

Illustration, Alloy B Alloy A Copper 3.4 3.3 Iron 0.8 0.9 Magnesium 0. 6 None Silicon 8.6 8.5

Zinc 1.0 O. Manganese. 0.2 minum Remainde Remainder I. Pressure die cast test bars were prepared as required for test A-STM E8-61T. A number of bars of each alloy were tested in the as cast condition; other were aged for 4 hours at C.; and others were aged for 8 hours TABLE I.-EFFECI OF AGING Ultimate Percent Alloy Tensile 0.2% Yield Elongation Strength M M As Cast:

A. (Invention Illustration)- 52, 330 34, 930 4. 3 B. (Comparison) 49, 250 25, 790 6. 0 Aged4 hrs. at 160 C.-

A 57, 920 43, 880 3. 4 B 49, 750 24, 840 5.6 A 58, 980 50, 370 2. 4 B t. 49, 260 26, 070 5. 4 Gain-8 hrs Aging:

A +6, 500 +15, 400 B None Negligible a negligible (Within the error of the test) gain in yield under these conditions. Castings described as first class.

II. Test bars were prepared by pressure die casting at two different temperatures. These bars were tested as in I above in the as cast condition. The results are set U.T.S., alloy A showed an improvement in yield where if anything, decreased in 0.2% yield strength.

TABLE II.EFFECT OF CASTING TEMPERATURE Ultimate 0.2% Percent Alloy (As Cast) Tensile Yield Elongation Strength iii/f III. A commercial producer of automotive steering gear housings was supplied an experimental amount of alloy A for a large scale test. Gear housings were pressure die cast at a temperature of 630-650 C. It was reported that the fluidity of alloy A was at least as good and probably better than that of the commercial aluminum alloy normally used by the producer; fill and tear were at least as good.

Quality control is maintained by means of a local impact test. The housings made from the regular alloy develop cracks, on the average, at 4 impacts. As cast housings made of alloy A cracked at 8-10 impacts. Heat aged housings made of alloy A cracked at 12-14 impacts.

Thus having described the invention, what is claimed is:

1. A pressure die cast aluminum alloy consisting of copper, about 1.5-6.0 weight percent; iron, about zero-2.5 weight percent; magnesium, about 0.15-1.0 weight percent; silicon about 5.0l3.0 weight percent, zinc, about Zero-2.5 weight percent and the remainder essentially only aluminum, said alloy being characterized by a substantial improvement in ultimate tensile strength and in yield strength after heat aging, a pressure die casting in the as cast condition at a temperature of between about 100 C. and about 200 C.

2. An article of manufacture comprising a pressure die cast structural configuration of aluminum alloy consisting of copper, about 3.0-4.0 weight percent, iron, about 0.7- 1.2 weight percent; magnesium, about 0.4-0.8 weight percent; silicon, about 7.5-9.5 Weight percent; Zinc, about 0.5-1.2 weight percent; and the remainder essentially only aluminum, which structure has been aged at a temperature of about 150-170 C. for a time of about 4-8 hours.

References Cited by the Examiner UNITED STATES PATENTS 2/1952 Willmore 75-l41 2/1958 Blackmun 148-325 OTHER REFERENCES Alloy Digest, A1-71, October 1958, Engineering Alloys Digest Inc., Upper Montclair, NJ.

HYLAND BIZOT, Primary Examiner. DAVID L. RECK, Examiner. C. N. LOVELL, Assistant Examiner. 

2. AN ARTICLE OF MANUFACTURE COMPRISING A PRESSURE DIE CAST STRUCTURAL CONFIGURATION OF ALUMINUM ALLOY CONSISTING OF COPPER, ABOUT 3.0-4.0 WEIGHT PERCENT, IRON, ABOUT 0.71.2 WEIGHT PERCENT; MANGNESIUM, ABOUT 0.4-0.8 WEIGHT PERCENT; SILICON, ABOUT 7.5-9.5 WEIGHT PERCENT; ZINC, ABOUT 0.5-1.2 WEIGHT PERCENT; AND THE REMAINDER ESSENTIALLY ONLY ALUMINUM, WHICH STRUCTURE HAS BEEN AGED AT A TEMPERATURE OF ABOUT 150*-170*C. FOR A TIME OF ABOUT 4-8 HOURS. 